In light curing apparatuses, especially for dental purposes, it has been known for long to use an optical fiber, to guide the light originating from the light source to the treatment site. The optical fiber may be formed as a light guide rod or as a light fiber rod, or also as a combination thereof.
Typically, as light sources, LED chips but also laser chips are used, which each emit a predetermined wavelength spectrum, and exciting the intermixed photo initiator, for example camphor chinone, in the dental restauration material that is to be hardened, to assure polymerization.
It is especially important for the polymerization to occur consistently. While, in dental restoration parts being located in a depth of some millimeters an appropriately longer polymerization time is selected, to also assure polymerization of the underlying regions, it is important for the polymerization to consistently occur even in horizontal direction, i.e. in a direction transversally to the emission axis of the light guide rod. Typically, the light emitted by the light source is collected, as it is known for example from U.S. Pat. No. 4,742,432 A1. Center-focusing and focusing of the emitted light beam will arise from this. Said center-focusing may not readily be seen with the naked eye, and thus the dentist relies on the light emission to consistently occur across the entire emissions area, for example in a circle diameter of 1 cm, even if this is not the case due to the center-focusing.
To counteract center-focusing and inconsistent illumination, it has been known for long to interpose mixing elements between the light guide rod or light fiber rod on the one hand and the light source on the other hand. As light mixing elements, for example glass elements comprising reflecting mini elements, which are evenly distributed in the glass elements, are used. Opacification of the glass element or other transparent element may be used to assure homogenization and diffusion.
Moreover, arrangement of ribs on the outside of the light mixing element has also be proposed, which essentially extend in the longitudinal direction of the light mixing element, i.e. essentially parallel to the direction of light. Depending on the rib angle, said longitudinal ribs create different reflections, especially due to the different diffraction indices between the surrounding air and the light mixing elements consisting of glass or other transparent plastic material.
It has also been proposed to metallize the ribs of the glass-mixing element by vapor deposition of a mirror layer, thus improving reflection effect.
Typically, the LED chips are arranged to have rectangular outer dimensions, or even are square in shape.
On the other hand, many different forms of the LED chip arrangement may be utilized depending on the desired power and configuration of the light curing apparatus, so that for optimum light mixing, different light mixing elements are required to be provided.
Moreover, light guide rods having diameters of 8 mm and 10 mm are provided. Accordingly, on the output side, provision of different light exit surfaces are to be taken into account, to assure loss-free light conduction, thus doubling the number of light mixing elements being required.
Moreover, rib mixer have already become known as homogenisers having different input and output forms. Such homogenisers typically comprise an input surface and an output surface auf and are filled with transparent material. Alternatively, they may also be formed as hollow elements. Said hollow elements suffer from the additional expenses and optical losses, which are generated by such a homogeniser as an ancillary part, so that such homogenisers, as a general rule, will not be employed.